1. Field of the Invention
The present disclosure relates to replacement data storage circuits, and more particularly, to replacement data storage circuits to store an address of a defective memory cell.
2. Description of the Related Art
For example, as disclosed in Japanese Laid-Open Patent Publication No. 11-238393, a nonvolatile memory device includes a redundancy circuit to replace a defective memory cell with a defect-free memory cell. The redundancy circuit stores replacement data (i.e., information about which memory cell is to be replaced) in a replacement data memory cell array. The redundancy circuit compares replacement data, which is read from the replacement data memory cell array, with a selected address, and performs a replacement operation on an address including a defective memory cell. Thus, the redundancy circuit needs a replacement data storage circuit including the replacement data memory cell array.
FIG. 5 is a diagram illustrating a typical replacement data storage circuit.
Referring to FIG. 5, a typical replacement data storage circuit includes a word line WL, a bit line BL, a replacement data memory cell array 11, a word line driver 12, a gate circuit 13, a sense amplifier 14, a latch circuit 15, and a control circuit 16. The replacement data memory cell array 11 includes a plurality of replacement data memory cells MC.
FIG. 6 is a timing diagram illustrating an operation of the typical replacement data storage circuit of FIG. 5.
Referring to FIG. 6, the typical replacement data storage circuit drives the word line WL when supplied with a power supply voltage VCC. Also, the typical replacement data storage circuit controls the gate circuit 13 when supplied with the power supply voltage VCC. That is, when supplied with the power supply voltage VCC, the typical replacement data storage circuit reads replacement data stored in the replacement data memory cell array 11. The read replacement data are transferred through the sensor amplifier 14 to the latch circuit 15.
However, when the power supply voltage VCC is supplied to the typical replacement data storage circuit, all the replacement data are transferred to the latch circuit. Thus, the amount of replacement data storable in the typical replacement data storage circuit may be restricted by the layout of a replacement data read circuit. Also, the typical replacement data storage circuit has low replacement efficiency.